What does the error message "too many parameters" mean?

TRIM produces this error as you try to fit a model with too many parameters i.e. more than 100 parameters (80 in earlier versions). This limit is reached in case of for example a time effects model with 20 years and a covariate with 5 categories. You have to try a simpler model, either by reducing the number of covariate categories or by running a linear trend model with less time points.